Distillation of tar



@Ct 9, 1934- s. P. MILLER DISTILLATION 0F TAR Filed Aug. e, 1929 2 sheets-snee#b INVENTOR MM Zi BY 2,# r /mnw ATTORNEYS x QQ x @ci 9, E934. s. P. MILLER 975243 DISTILLATION 0F TAR Filed Au'g. 6, 1929 2 Sheets-Sheet 2 bm@ fun-"d ATTORN EYS Patented Oct. 9, 1934 PATENT OFFICE DISTILLATION OF TAR Stuart Parmelee Miller, Englewood, N. J., assigner to The Barrett Company, New York, N. Y., a corporation of New Jersey Application August 6, 1929, Serial No. 383,858

23Claims.

This invention relates to a process of distilling tar and the production of a distillate of high tar acid content. The invention includes both 5 the process and apparatus for carrying it out.

The invention is of particular value in connection with the operation of a coal distillation plant operated in conjunction with a steel plant or at other places where there is a large demand for liquid fuel as Well as coke. At coal distillation plants operated in connection with steel plants, the production of tar is often in excess of what can be burned as fuel. The invention can be applied in such instances to distill the tar and proo duce an oil of high tar acid content and simultaneously produce a blended oil pitch mixture suitable for fuel. The invention provides a profitable process under these and other circumstances. The process of this invention includes a rectifying operation followed by fractional condensation; it also includes refluxing of distillate from the fractional condensers thru the rectifying column to remove from the gases passing thru the n: rectifying column oils of higher boiling range and permits chiey only oils of high tar acid content with a boiling range under a predetermined maximum to pass over to the condensing system.

The distilling operation according to a pre- .,O ferred form of the invention comprises two stages. In the first stage tar which has been partially distilled in the second stage is further distilled to produce pitch. This stage of the distillation is eccted by spraying the tar into hot gases. 5 preferably hot coal distillation gases which already contain in vapor form oils derived from the destructive distillation or decomposition 'of the coal. Coal distillation gases are advantageously employed at substantially the temperature at which they leave the ovens. retorts. etc. in which they are formed and while they still retain suhstantiallv their original vapor content, i. e. before.

any appreciable amount of tar or oils has been separated from the gases. By spraying the gases an intense spray of tar so that the gases are quickLv cooled. gases hot enough to coke the pitch formed may be used to advantage and without any appreciable amount of coke being formed. By using the gases at such high tem- .J peratures the capacity of the apparatus is increased and the rectification and recovery of oils from the gases are improved. The tar and the gases, especially where gases of high temperature are employed. are advantageously admitted to one end of the still and pass thru the still in a concurrent direction with spraying and respraying of the tar into the gases and progressive distillation of the tar to pitch. The spraying of the gases is such as to remove any entrained pitch particles from the gases when pitch-laden gases..such as hot coal distillation gases, are employed for the distillation. Y

In the second stage of the distillation process. the hot gases and vapors from the still pass thru a hot gas saturatcr Where they are sprayed with tar. When the gases leaving the stillare notI saturated with lower boiling constituents they may advantageously be further employed for the partial distillation of tar, as in a saturating chamber or saturator in which they are brought into further intimate contact with the tar, and the vapor content of the gases. especially the content of vapors of lower boiling oils may thus be increased. During this partial distillation of the tar. vthe gases are somewhat cooled but the cooling is not such as to produce any undesirable condensation of vapors from the gases. The partially distilled tar from the saturator is advantageously fed to the still for further distillation. In the saturator the vapor content of the gases is increased beyond that which can advantageously be obtained in the still. By thus increasing the vapor contentof the gases. the quantity of hot gases required for the distillation of the tar is reduced and consequently the loss of distillate as vapors in the gasesleaving the condensing system is reduced. Other savings incident to the use of a saturator to increase the oil content of the gases passed thru the rectifying column and condensers include the saving incident to the installation and upkeep of a smallerl plant than would otherwise be required.

The gases and vapors from the still or from the saturator where one is employed. are passed thru a rectifying column and then to a fractional condensing system. The highest boiling oil fraction is returned to the rectifying column to eiect rectiication of the distillate. The cooling of the gases in this condenser in which the highest boiling fraction of distillate is separated from the gases, is advantageously eiected by indirect contact with a cooling medium. The cooling medium may advantageously be tar which is simultaneously heated with the cooling of the gases and the preheated tarv may then be fed to the still or to the saturator for distillation. A vapor chamber 'may be located between the tar preheater and still or saturator where desired to remove a separate distillate fraction. and the distillation residue m11 then be fed to the sun or sauuawr. 119

According to one advantageous procedure, the tar is preheated in a heat interchanger in which a high boiling oil fraction is simultaneously separated from the gases and vapors leaving the rectifying column. The preheated tar is then sprayed into the hot gas saturator and the residue from the saturator, comprising partly distilled tar, is then fed to the still for further distillation to produce pitch.

In the rectifying column, oils boiling below a predetermined maximum, which are contained in the fraction of distillate fed to the rectifying column, are vaporized and returned to the condensing system. Likewise, oils boiling above this predetermined boiling range, which are present as vapors in the gases and vapors leaving the saturator, are to large extent condensed in the rectifying column and although a portion of these higher boiling oils may leave the rectifying column in vapor form, they are for the most part condensed in the first fractional condenser and are returned to the rectifying column. The predetermined maximum boiling range of the oils which pass to the condensing system is so selected that the oils boiling above this predetermined boiling range which remain in liquid form in the rectifying column, are oils of low tar acid content. With proper regulation of the vapor content of the gases may be thus retained as liquid in the column. They are drawn off the bottom of the rectifying column and may advantageously be blended with the pitch from the still to produce fuel pitch. The vapors leaving the rectifying column are rich in tar acids and an oil fraction containing as high as 2025% of tar acids may normally be separated in the fractional condensers. 'Ihe tar acid content of the fraction or fractions will, of course, depend upon the content of tar acids in the tar being distilled and also upon the character of the tar acids. From tars containing high percentages of tar acids, e. g. 7-9% of the usual tar acidsr found in coal tar, oil fractions containing more than 25% tar acids may readily be obtained.

The condensing system comprises means for collecting at least two distillate fractions. The highest boiling fraction is returned to the rectifying column. More than two oil fractions may be recovered from the gases to advantage, especially where the distillate is of such a nature that the oils boiling below the predetermined boiling range of the vapors carried by the gases leaving the first condenser may be divided into fractions of widely different tar acid content, and the fractions of lower tar acid content may then be returned to the rectifying column together with the oils from the first condenser or they may be separately collected and treated in any desired manner.

The fractions of higher tar acid content, and where only two distillate fractions are obtained, all of the lower boiling fraction are separately collected as the high tar acid product of the process. This product may be treated in the usual manner for the recovery of tar acids e. g. by extraction with caustic solution. The neutral oil remaining after the extraction of the tar acids may be blended into the fuel pitch or may be disposed of in any suitable way. The tar acid oils may be separately collected and sold or used as such.

The higher boiling oils from the rectifying column may be separately collected and disposed of in any desired manner. Where a large quantity of fuel is required, as where a coke oven plant is operated in conjunction with a steel works, this high boiling oil fraction is advantageously blended with the pitch produced to make a fuel pitch. Where a high melting point pitch has been produced, special means should be provided for blending the pitch with the heavy oil and care should be taken to produce a homogeneous blend. Where a pitch of lower melting point is produced in the still, the usual means for blending pitch with oil may be utilized. The pitch is preferably blended with the oil in the hot fluid condition in which it is drawn off of the still.

Hot gases of Various kinds may be employed for distilling the tar according to this invention. Hot coal gasification gases may be used to advantage; as, for example, hot coke oven gases, hot retort gases, hot water gas, hot producer gas, etc. Where hot pitch-laden gases, such as hot coke oven gases, are employed for the distillation, the tar is sprayed into the gases in the still in the form of a fine intense tar spray which scrubs and substantially detars the gases simultaneously with the distillation of the tar to produce pitch.

Various tars may be distilled according to this invention but the invention is more particularly adapted to the distillation of coke oven tar or other tar of high tar acid content. The tar acid content of coke oven tar, for example, may vary, depending upon the character of the coal coked, upon the temperature at which the coal is coked and the coking cycle and the treatment of the coke oven gases from which the tar is recovered, etc. 'Ihe present invention is su'ciently flexible to provide for the treatment of various tars to recover tar acids and where desirable to produce fuel pitch.

The invention will be described in connection With the accompanying drawings, but it is intended and is to be understood that it is not limited thereto.

In the drawings,

Fig. 1 is a plan view of a coke ovenl plant equipped for carrying out the process of this invention;

Fig. 2 is an elevation partly in section of the apparatus of Fig. 1; and

Fig. 3 is a section on the line 3 3 of Fig. 2.

In the drawings, 5 is a coke oven battery. Each of the ovens of the battery is connected with the collector main 6 by uptake pipes and goose-necks 7. The cross-over main 8 connects the collector main with condensers, etc., not shown. This apparatus may be of the usual type and is shown more or less diagrammatically.

At the opposite side of the battery uptake pipes and goose-necks 11 connect selected ovens of the battery with the hot gas header 12. By the proper manipulation of valves in the uptake pipes 7 and the uptake pipes 11, gases from these selected ovens may be passed either to the collector main 6 or thru the hot gas header 12 into the still-10.

In the still is means for producing a fine intense spray of tar or partially distilled tar or pitch in the gases. This comprises a roll 13 which dips slightly into the tar or pitch and which is adapted to be rotated at a high speed by the motor 14. The roll is advantageously located at one side of the still as shown in Fig. 3. By rotating the roll at a speed of, for example, 900-1200 R. P. M., a fine intense spray of tar or pitch is produced in the gases and the tar or pitch is washed over the walls of the still and keeps them free fromq accumulations of coke or other solid deposit. 'I'he lli) Although a pitch of higher melting point mayA be produced in the still, in which case a higher percentage of condensable constituents Will be carried over to rthe condensers by the gases, according to this invention, a pitch with a melting point in the neighborhood of 150 to 160 or 170 F. is produced in the still. The pitch is drawn oif into suitable collecting means 17, and where fuel pitch is to be produced it is fed thru the vpipe 18 to the mixing tank 19 for blending with the distillate oil. Where a high melting point pitch is produced, special means for handling the pitch may be required to keep it hot and thinly lfluid or it may be allowed to solidify immediately it leaves the still.

The gases and vapors leaving the still 10 pass up thru the hot gas saturator 20. Tar is sprayed into the gases thru the nozzle 21. Baling means 22 is provided to expose a large surface of the tar to the action of the hot gases and vapors and to remove from the gases entrained particles of tar spray which may be carried from the still. The distillation residue which is a partly distilled tar-is drawn oi thru the line 23 and fed to the end of the still 10 at which the hot gas header 12 enters. This partially distilled tar and the hot gases pass thru the still in a concurrent direction and pitch of the desired melting point is produced.

From the hot gas saturator the gases and vapors pass thru the rectifying column 25. 'I'his is advantageously packed with Raschig rings or other suitable baling means indicated at 26. From the rectifying column the gases pass to the condensing system. The first condenser is advantageously an indirect condenser and is preferably located above the rectifying column 25( As shown in the drawings at 27, the oils removed in the condenser are fed by gravity to the rectifying` column 26. Tar supplied at 28 serves as the cooling medium. This tar ows thru the coil 29 in indirect heat interchange relation with the hot gases and vapors and simultaneously with the separation of oils from the gases the tar is preheated. This preheated tar is supplied thru the line 30 to the nozzle 21 in the hot gas saturator.

From the condenser 27 the gases pass to further condensers for the recovery of the tar-acidcontaining oils. Any suitable type of condensers may be employed. An indirect fractional condensing system is shown which is suited for the recovery of separate oil fractions and is so regulated that the oils containing the highest percentage of tar acids are collected in separate fractions. Other condensing means which may involve either direct or indirect contact with a cooling medium may be employed. The condensers 31, 32 and 33 shown in the drawings are more or less diagrammatic and provide for drawing oi three separate oil fractions at 34, 35 and 36, and 34', 35', and 36'. The gases pass thru the exhauster 37 to means for the recovery of ammonia, etc. not shown.

They oil fractions high in tar acids may be shipped to another plant for the recovery of tar acids or may be drawn olf thru the line 38 to the tar acid.- extractor 39 directly. The fractions lower in tar acids are drawn off thru the line 40 into the tank 41. These oils-may be pumped by the pump 42 thru the line 43 into the rectifying column and be sprayed therein thru the nozzle 44 or they may be pumped thru the line 45 and fed to the still 10, or they may be drawn 01T separately. Supplying these oils of low boiling rangel to the still lowers the temperature of the gases passing thru the still and thus regulates the distilling operation. Spraying these oils into the rectifying column cools the gases passingk therethrough and increases the quantity of heavy oils drawn olf.

The heavy oils which separate from the gases in the rectifying column and the higher boiling oils present in the oils added to the rectifying column and not distilled in the hot gases and vapors are drawn off at the bottom of the rectifying column thru the line 50. Where a fuel pitch is to be produced, these heavy oils are advantageously drawn oi directly to the mixing tank 19. The mixing tank 19 is provided with agitating means 51, and a condenser 52 is employed with advantage for returning distillate produced during the blending operation. The fuel pitch produced by blending the pitch and heavy cil is drawn oi into the tank 53 where it is maintained in a heated condition by the steam coil 54 until duced. These are Water-soluble and separate from the remaining neutral oil in the decanter 62. 'I'he neutral oil is drawn off into the tank 63 and the phenolates are drawn off into the tank 64. These may be worked up inthe usual manner for their tar acid content. The neutral oils may be supplied from the tank 63 to thetank 19 thru the line 65 and used in the blended fuel pitch.

To produce tar acids with rectification and recovery of a heavy oil and pitch, the tarmay be distilled and the distillate divided into fractions so that approximately 60% of the tar remains in the still and is drawn off as pitch, approximately 15% of the oils are drawn of the rectifying column 25 and approximately 25% of the oils are carried forward into the condensing system to be collected as tar acid oils.

Although other hot gases, and especially hot Waste gases such as producer gas, water gas, etc., may be employed for the distillation of tar and recovery of tar acids and also fuel pitch, this invention is more particularly adapted to the distillation of tar in hot coke oven gases at a coke oven plant operated in conjunction with a steel plant where the fuel pitch produced may be employed as fuel in the steel works.

Inclaim:

1. The methodof distilling tar and producing an oil of high tar acid content which comprises distilling tar by direct contact with hot gases,4

and producing a pitch with a melting point of 150 to 170 F. therefrom, passing the resulting gases and vapors through a rectifying column, and

then through a fractional condensing system,

content in the subsequent portion of the fractional condensing system.

2. The method of distilling tar and producing an oil of high tar acid content which comprises distilling preheated tar by direct contact with hot gases, and producing a pitch with a melting point of 150 to 170 F. therefrom, passing the resulting gases and vapors through a rectifying column, and then through a heat interchanger, condensing oils of relatively high boiling range and low tar acid content in the heat interchanger by indirect contact with tar, passing the tar thus preheated to the zone of distillation, returning the oils to the rectifying column, passing the gases and vapors from the heat interchanger to a condensing system, and further cooling them to condense oils of relatively low boiling range and high tar acid content.

3. The method of distilling tar to produce pitch and an oil of high tar acid content which comprises distilling the tar to pitch, passing the resulting gases and vapors through a rectifying column, fractionally cooling the gases and refluxing a portion of the condensate so as torecover lower boiling oils of high tar acid content and to recover approximately three-eighths of the vapor content of the gases as a relatively heavy oil from the rectifying column, substantially free from tar acids.

4. The method of vproducing fuel pitch, which comprises distilling tar to pitch by spraying tar into hot coal distillation gases, whereby the tar is distilled to pitch and the gases are substantially detarred and a pitch product is obtained containing constituents originally present in the coal distillation gases and constituents originally present in the tar, partially cooling the resulting gases and vapors in a rectifying column by bringing them into direct contact with an oil therein, recovering from the rectifying column a heavy oil which comprises constituents originally present in the coal distillation gases and constituents originally present in the tar and blending the heavy oil with the pitch to produce a fuel pitch.

5. The method of distilling tar to produce an oil of high tar acid content 'and a fuel pitch, which comprises distilling tar to pitch by direct contact with hot gases in a still, spraying tar into the resulting gases and vapors to partially distill the tar and enrich the gases in lower boiling onstituents, passing the gases through a rectifying column and then to a fractional condensing system, regulating the cooling of the gases so as to obtain a low boiling oil of high 'tar acid content and an oil of higher boiling range, returning the oil of higher boiling range to the rectifying column and using it therein for the rectification of the vapors in the gases, and blending with the pitch from the still the residue of non-volatilized oil from the rectification.

6. The method of distilling tar to produce an oil of high tar acid content and a fuel pitch, which comprises spraying tar into hot coal distillation gases in a still to distill the tar to pitch and substantially detar the gases and thereby producing a pitch comprising constituents originally present in the hot gases and constituents originally present in the tar, spraying the resulting gases and vapors with tar and thus partially distilling the tar, feeding this partially distilled tar to the still for distillation to4 pitch, passing the resulting gases and vapors through a rectifying column and then through a condensing system, recovering a plurality of distillate fractions in the condensing system, returning the highest boiling fractionto the rectifying column, blending with the pitch the residue of non-volatized oil from the rectifying column which includes constituents originally present in the hot gases and constituents originally present in the tar to produce a fuel pitch, and collecting distillate fractions with a high tar acid content without mixing with fractions of low tar acid content.

7. I'he method of distilling tar to produce an oil of high tar acid content and a fuel pitch, which comprises distilling tar by direct contact with hot coke oven gases to produce a pitch with a melting point of about 150-160 F., spraying the resulting gases and vapors with tar. to partially distill the tar, passing the resulting gases and vapors through a rectifying column and then to a fractional condensing system, rectifying the vapors in the rectifying column by contact with oil from the condensing system, blending the residue of non-volatized oil from this rectifying column with the pitch to produce a fuel pitch, and collecting at least one distillate fraction of high tar acid. content without mixing with fractions of low tar acid content. l

8. The method of distilling tar to produce an oil of high tar acid content and pitch, which comprises distilling partially distilled tar further to pitch with a melting point in the neighborhood of 150-170 F. in hot coke oven gases,vwhile spraying the partially distilled tar into the hot gases in such a Way as to substantially detar the gases, partially distilling tar by direct contact with the resulting hot gases and vapors, in a saturating chamber passing the resulting gases and vapors n through a rectifying column and then through a heat interchanger to preheat the tar and separate oils from the gases, supplying the oils to the rectifying column, spraying the preheated tar into the gases and vapors in the saturator to partially distill the tar, and feeding this partially distilled tar to the still while controlling the temperature of the gases and vapors leaving the heat interchanger so as to return to the rectifying column oils of relatively high boiling range and low tar acid content and separately collecting a fraction of relatively low boiling range and high tar acid content.

9. 'I'he method of distilling tar and producing a fuel pitch', which comprises distilling tar to pitch of a melting point of about 150-160 F. by spraying the tar into hot gases and passing the resulting gases and vapors through a hot gas saturator and spraying tar therein to partially distill the tar, passing the resulting gases and vapors through a rectifying column and then through a fractional condenser, rectifying vapors in the rectifying column with oil from the condenser and blending heavy oils from the rectifying column with the pitch to produce a fuel pitch.

10. A still, means for passing hot gases therethrough, a tar feed to the still, agitating means in the still, a pitch draw-off from the still, a rectifying column through which the gases and vapors from the still pass, and a mixing tank with means for supplying pitch from the still and heavy Oil from the rectifying column thereto.

11. A still, means for passing hot gases therethrough, a tar feed to the still, means for spraying the tar into the gases passing through the still in such manner as to bring substantially all portions of the gases into contact with tar spray, a pitch draw-on' from the still, a rectifying column through which the gases and vapors from the still pass, condensers beyond the rectifying column, means for supplying a portion of the oil from the condensers to the rectifying column, and means for separately withdrawing another portion of the oil from the condensers.

12. A still, means for passing hot gases therethrough. a tar feed to the still, means for spraying the tar into the gases passing through the still in such manner as to bring substantially all portions of the gases into contact with tar spray, a pitch draw-off from the still, a rectifying column through which the gases and vapors from the still pass,` a heat interchanger and condensers to cool the gases coming from the rectifying column, means for supplying oil separated in the heat interchanger to the rectifying column, and means for withdrawing oil from the condensers.

13. A still, means for admitting hot gases and tar to the still, a mixing tank, means for drawing pitch from the still and feeding it to the miinng tank, a hot gas saturator, means for passing the gases and vapors from the still into the hot gas saturator, a rectifylng column, means for passing the hot gases and vapors from the saturator to the rectifying column, an oil feed to the rectifying column and a draw-off from the rectifying column to the mixing tank.

14. A still, means for admitting hot gases and tar to the still, a mixing tank, means for drawing pitch from the still and feeding it to the mixing tank, a hot gas saturator, means for passing the gases and vapors from the still into the hot gas saturator, a rectifying column, means for passing the hot gases and vapors from the saturator to the rectifying column, an oil feed to the rectifying column and a draw-oi from the rectifying column to the mixing tank, and a condensing system and means for supplying oil from the condensing system to the rectifying column.

15. A still, means for admitting hot gases and tar to the stl, a mixing tank, means for drawing pitch from the still and feeding it to the mixing tank, a hot gas saturator, means for passing the gases and vapors from the still into the hot gas saturator, a rectifying column, means for passing the hot' gases and vapors from the saturator to the rectifying column, an oil feed to the rectifying column and a draw-oi from the rectifying column to the mixing tank, and a heat interchanger for partially cooling the gases and vapors from the rectifying column and for supplying oil separated from thegases in this heat interchanger to the rectifying column.

16. In combination with a coke oven battery, a still, agitating means therein, means for passing hot fresh coke oven gases directly from ovens of the battery tothe still, a hot gas saturator, a rectifying column, a heat interchanger and condensers through which the gases and vapors from the still pass in succession, means for supplying tar to the heat interchanger and then to the saturator, means for supplying distillation residue from the saturator to the still, means for returning oils condensed in the heat interchanger to' the rectifying column, a mixing tank, and means for supplying pitch from the still and heavy oil from the rectifying column to the mixing tank.

17. The method of producing a. blended pitch product which comprises distilling tar to pitch by spraying tar` into hot coal distillation gases, whereby the tar is distilled to pitch and the gases are substantially detarred and a pitch vproduct; is obtained which contains constituents originally present in the coal distillation gases and constituents originally present in the tar, partially cooling the resulting gases and vapors in a rectifying column by bringing them into direct contact with an oil therein, recovering from the rectifying column a heavy oil which comprises constituents originally present in the coal distillation gases and constituents originally present in the tar and blending the heaW oil with the pitch to produce a blended pitch product.

18. The method of distilling tar to produce pitch and an oil of high tar acid content which comprises distilling tar to pitch by direct contact with hot gases. spraying tar into the resulting gases and vapors, subjecting the resulting gases and vapors to rectification and then cooling them to separate distillate of higher boiling range and distillate of lower boiling range and high tar acid content and passing the distillate of higher boiling range into contact with the gases and vapors in the rectification.

19. The method of distilling tar to produce pitch and an oil of high tar acid content which comprises distilling tar to pitch by direct contact with hot gases, spraying tar into the resulting gases and vapors, subjecting the resulting gases and vapors to rectication and then cooling them to separate distillate of higher boiling range and distillate of lower boiling range and high tar acid content, passing the distillate of higher boiling range into contact with the gases and vapors in the rectication. and blending the oil residue from the rectification with the pitch obtained by the distillation of the tar.

20. The method of distilling tar to produce an oil of high tar acid content which comprises distilling tar to pitch by bringing the tar into direct contact with hot inert gases, withdrawing the resultant gases and vapors from contact with the tar and subjecting them to rectification, cooling the resulting gases and vapors to separate first an oil of higher boiling range and then an oil of high tar acid content and contacting the oil of higher boiling range with the gases and vapors in the rectification.

21. The method of distilling tar to produce pitch and an oil of high tar acid content which comprises distilling the tar by bringing the tar into direct contact with hot coal distillation gases, thereby producing a pitch product containing constituents originally present in the coal distillation gases and constituents originally present in the tar, subjecting the resulting gases and vapors to rectication, cooling the rectified gases to separate iirst an oil of higherboiling range and then an oil of high acid content which comprises constituents originally present in the coal distillation gases and constituents originally present in the tar, contacting the oil of higher boiling range with the gases and vapors in the rectication. and blending the residue from the rectiiication `with the pitch.

22. The method of distilling tar and producing an oil of high tar acid content which comprises distilling tar to pitch by spraying the tar into hot coal distillation gases thereby producing a pitch containing constituents originally present in the coal distillation gases and constituents originally present in the tar, subjecting the gases and vapors resulting from the distillation to rectification, cooling the rectied gases and vapors to separate first an oil of higher boiling range containing constituents originally present in the coal distillation gases and constituents originally present in the tar, andthen an oil of high tar acid content, and contacting the oil of the gases, thereby separating higher boiling constituents from lower boiling constituents which remain in vapor form and then blending with the pitch the higher boiling constituents separated from the gases.

STUART PARMELEE NHLLER. 

